1. Technical Field
The invention relates to technologies for achieving automation of orientation work at the preceding stage of making three-dimensional measurement from different camera positions, automatic acquisition of initial values for stereo matching, and automation of the three-dimensional measurement.
2. Prior Art
In performing three-dimensional measurement in close-range photogrammetry the measurement is carried out through the flow of processes as shown in FIG. 1. Namely, it is required to perform processes of taking a pair of stereo images of a subject (a)→position detection (b)→orientation (c)→stereo model formation (d)→three-dimensional measurement (e). Although these processes are performed mainly by operations of a computer, the processes of the position detection (b) and the three-dimensional measurement (e) have so far been performed manually. The position detection (b) is a preprocess of the orientation, which is a process to obtain position, inclination, and the like of the cameras for taking images.
By obtaining the relative position between the cameras and the subject in the process of the orientation (c), it becomes possible to form a stereo model providing a stereo view and achieve the three-dimensional measurement. The process of the position detection (b) preceding the orientation (c) is such work as to obtain coordinate positions, on each camera, of six or more corresponding points taken by separate cameras.
In the three-dimensional measurement (e), there are two kinds: point measurement and planar measurement.
In the case of the point measurement, the point to be measured on the subject is generally measured manually. However, when automatic measurement is planned or improvement in accuracy is desired, it is practiced to glue a mark onto the subject.
In the case of the planar measurement, automatic measurement is carried out by using a method of stereo matching through image processing. Then, however, it was required to make such initial setting as determination of a template image and setting up of the searched width through manual work.
In the work of the position detection (b), the operator selects six or more points of measurement on the subject in the left and right images and, while observing each image, correlates the points of measurement on the subject with each other and detects the coordinates of the positions. However, since the operator basically had to do such work while taking a stereo view, it required skill and, in addition, it was complicated, difficult, and problematic.
Especially, in such work as to correlate the left and right images with each other upon determination of the points of measurement and detect the detailed coordinates of the positions, personal errors were liable to occur, results were different from operator to operator, and sufficient accuracy was difficult to obtain. There were even cases where such measurement was unachievable by some operators. To obviate the difficulties, such a method as to glue a mark onto the subject is sometimes practiced.
However, it is an unfavorable thing for such work as gluing a mark onto the subject to increase, and there are even such cases where, depending on the subjects, gluing a mark onto the subject is very difficult. Therefore, this method has not come into wide use.
There is also such a method to perform three-dimensional measurement with two cameras firmly fixed onto a stereo pan tilt head thereby eliminating the orientation work.
In this case, however, there should absolutely be no deviation in the relative position between two cameras on the pan tilt head, and therefore the measurement environment and the subject for measurement are greatly limited. At the same time, such apparatus becomes large, heavy, and difficult to handle and, besides, expensive. Hence, this method also is not used so widely.
Further, in the point measurement in the three-dimensional measurement (e), when a mark or the like is not glued onto the subject for measurement, the operator had to indicate the point of measurement while observing the taken image in the course of the measurement. Therefore, much labor and time were required when there were many points of measurement. Further, when it was attempted to make precise measurement, personal errors were liable to occur and, in the worst case, measurement itself became unachievable.
Such things as described above can be obviated if measurement is carried out after gluing a mark onto a subject, but in that case, as described above, the labor for attaching the mark was newly required and, depending on the subjects, it was difficult to glue a mark onto the subject and sometimes it became impossible to make measurement.
In the case of the planar measurement, it was required to manually make such work as to determine the template image and determine an optimum searched width as a preprocess in making automatic measurement through stereo matching. Further, when mismatched points or the like occurred, correction had to be made manually. Thus, it was difficult to realize automation.